abx targetting energy metabolism + ABX presentations + mock exam shit

demands for new abx for TB(6)

efficacy/rapid action → shorten treatment; selectivity, lack of toxicity; bioavailability, intermittent treatment; active on (almost) all individuals in all bacterial population; specific, well understood (new) mechanism of action; synergistic action in drug combinations

cytochrome bc1 as target descr

imidazopyridines - found by large scale screening, slowly improved over years (decrease toxicity, etc)

what influences sensitivity for imidazopyridines

mutations in cyt bc1 - overexpression of cyt bc1 subunits decreases sensitivity - thought it meant that it was the target, more evidence needed to conclude that though, with other studies figured out that bc compounds decrease cellular ATP levels - action related to energy metabolism

other possible target for TB

ATP synthase as target - found through phenotypic HTS, diarylquinolines (eg bedaquiline!)

issue w/ some bacteria (esp mtb)

biofilm/dormant bacteria - low metabolic activity, intert to most abx, resuscitation problematic, unsure how energy metabolism works

how does energy metabolism work in dormant bacteria, how figure out?

grow bacteria in in vitro dormancy system, energy metabolism still active - SO drugs blocking energy metabolism can also kill dormant bacteria

surprising thing w/ bedaquiline

delay in killing - bc sufficient depletion of ATP pools necessary to interfere w/ bacterial viability, doesnt work immediately

explanation of delay?

mtb respons to blocking energy metabolism w/ transcriptome, proteome response - observe at level of target protein, pathway, metabolites and whole bacteria

transcriptomics of ATP synthase inhibition (2)

upregulation of ATP synthase, upregulation of dormancy response

proteomics of ATP synthase inhibition

upragulation of ATP synthase, upregulation of alternative energy pathways (eg cytochrome bd), downregulation of biosynthesis pathways (DNA, protein, lipids) → save energy

how to enhance potency of ATP synthase inhibitors

use host derived fatty acids as an energy source

4 ways BDQ kills

unsure - hypotheses: ATP level decrease, delta pH decrease, ATP synthase-dependent uncoupling, H+/K+ antiporter

where is BDQ resistance gene (2)

AtpE gene - altered ATP synthase c subunit → decrease D+BDQ binding which decreases drug activity
Rv0678 - repressor of MmpS5-MmpR5 - loss of function mutation - decreases repression - increases effluc pump which decrease intracellular BDQ

target of BDQ

F0C subunit of ATP synthase

what gives low level BDQ resistance

PepQ - by unknown mechanism

what type of abx is moxifloxacin?

4th gen synthetic fluoroquinolone

how is the activity of moxifloxacin

broad spectrum activity - against gram+ and gram- and atypical pathogens

what did the structural changes allow for w/ moxifloxacin

drug to physically trap the DNA gyrase cleavage complex, completely blocking bacterial DNA replication

mode of action of moxifloxacin

inhibits bacterial DNA gyrase and topoisomerase, more effective against gram+ than gram-

how can moxifloxacin be taken

orally and IV

what is the PK profile of moxifloxacin ideal for

treating respiratory infections (like TB) - much higher penetration of lung tissue than blood plasma

did moxifloxacin deliver on its promise

no :(( did not deliver shorter human treatment but is safe!

why is moxifloxacin not 1st line drug

QT prolongation - increased risk of cardiac arrhythmias, also other serious side effects, other, safer abx preferred when available

resistance to moxifloxacin

mutation in gyrA - encodes part of DNA gyrase, mutation in quinolone resistance determining region - reduces abx effectiveness, do not explain all cases of reduced fluoroquinolone susceptibility

3 ways of detecting resistance to moxifloxacin

phenotypic methods - MGIT (mycobacteria growth indicator tube - detects bacterial growth through changes in fluorescence related to oxygen consumption), BACTEC (detects bacterial metabolic activity by measuring radioactive CO2 production)
molecular method - MPAC - PCR based analysis to find gyrA mutations

source of rifampicin

semi synthetic - discovered by modifying natural compounds found in soil

possible side effect of rifampicin

elevated levels of Cyt P450 in the liver - can lead to liver dysfunction, patients kept under close monitoring

mode of action of rifampicin

inhibits bacterial DNA dependent RNA polymerase - enzyme responsible for transcribing DNA into RNA; w/ steric occlusion - physically blocks the pathway of the growing RNA strand

how to get rifampicin resistance

RNA polymerase alteration creates resistance, mutations in the rpoB gene - then rifampicin cannot inhibit RNA polymerase

With what mechanism can Gram-negative bacteria reduce influx of hydrophilic antibiotics?

By decreasing expression of general diffusion porins

Which of the following statements concerning infection studies and antibiotic screens with zebrafish larvae is FALSE?
One can test for sterilizing concentrations of compounds

One can determine if compounds work in vitro

One can determine the effect of treatment on infection using fluorescent bacteria and microscopy

One can identify synergistic effects of multiple compounds

One can determine if compounds work in vitro

One can determine if compounds work in vitro

Bacterial infections can lead to septic shock caused by disproportional activation of Toll-like receptors. Which statement is correct?

During septic shock the NFkB pathway can be over activated via TLR4 receptors, NFkB inhibitors are therefore a good potential drug target for the treatment of septic shock.

You wish to determine the target of a new antibiotic compound. In a pilot experiment you find that a certain concentration of the antibiotic inhibits activity of enzyme A. Your hypothesis is that enzyme A may be the target of this antibiotic. What would you do to support this hypothesis?

Test if the antibiotic can inhibit enzyme A in a dose-dependent manner

Clofazimine is an anti-tuberculosis drug that interacts with the bacterial respiratory chain. However, clofazimine does not strongly inhibit respiratory chain function in bacteria. What is the function of clofazimine in the respiratory chain?

Clofazimine transfers electrons from NADH dehydrogenase onto molecular oxygen

Which of the following statements is true for antibiotics that have a time-dependent killing?
Of all drugs they are generally most dependent on AUC:MIC

They usually have a saturable killing effect

Of all drugs they generally have the lowest MIC

They usually have a long post-antibiotic effect

They usually have a saturable killing effect

Which persons are usually enrolled in phase II clinical trials?

Patients who are not paid for their participation